Pollination and plant reproduction in the Cerrado, the world's most biodiverse savanna.

The Brazilian Cerrado is a continental-wide biodiversity hotspot and the most species-rich savanna ecosystem in the world. The main aspect characterising this biodiversity is that the landscape is arranged as an intricate mosaic of different plant formations, including grasslands, savannas, and forests, each harbouring distinct but interconnected communities. Seasonality and natural fires are key and ancient natural factors in the biome, with organisms showing many adaptations. The Cerrado is also home to millions of people, and the essential ecosystem services provided for agricultural production make it one of the world's major crop regions. However, it has undergone intense destruction in the last decades, with conservation concerns historically overshadowed by the neighbouring Amazonia and Atlantic Forest biomes. Considering the importance of pollination and plant reproduction for maintaining terrestrial ecosystems, we synthesise the known information for the Cerrado as an illustrative example that could be applied to other megadiverse ecosystems worldwide. Although apomixis (asexual seed formation) and self-pollination mechanisms occur to a lesser extent, most plants in the Cerrado require biotic pollination. For instance, this is the case for some dioecious and monoecious species. However, the majority of plants have bisexual flowers, with the frequency of self-incompatibility increasing towards denser plant formations such as forests, illustrating differences in dependency on pollination across habitats. Many Cerrado plants adopt strategies favouring outcrossing, including distyly, enantiostyly, heteranthery, and dichogamy. Although plant-pollinator interaction networks are mostly generalised, the pollinators are organised into guilds, with bees pollinating most plants and using several resources. Other common guilds include beetles, moths, hummingbirds, and bats. Importantly, flowering phenology peaks across plant formations at different times of the year, creating habitat complementarity across the vegetation mosaic that continuously sustains transiting pollinators. Thus, the interaction between plants and pollinators connects and is sustained by landscape complexity, which should be regarded as essential for ecosystem conservation. In this context, periodic fires that trigger massive flowering and promote biomass reduction are an essential natural disturbance that maintains the diversity of open landscapes. The interdependence of plants and pollinators in the face of the ongoing destruction of the Cerrado adds another challenge for its conservation, and highlights the necessity for conserving complementary habitats at the landscape level. While forest formations are granted protection by law, these alone are insufficient to maintain high pollinator diversity, with potential cascading effects on the ecosystem services they provide and requiring the maintenance of the neglected grasslands and savannas. Thus, the simultaneous conservation and restoration of the mosaic plant formations across the landscape will be crucial for the future of the Cerrado.